yep, according to that BW image it's missing some contrast.
Where I'd put some extra:
- upper part of the chest (where it's already shaded, just add a bit more)
- legs, glaze both to be darker (all parts get to be darker a bit, highlights, midtones, shadows)
- left arm the muscle under the arm to be darker AND if you want some extra, then the other muscles could get a glaze or 2 on their underside.
you could also 'cheat' a bit by making the back and top of the head lighter (current color + white or a greenish-yellow).
color for the glazes: basically what you want, but a dark blue (actually the blue mixed in the green) or a dark reddish brown would looks super. Or if you don't want those colors a dark-green/black-green (WnN green ink / VGC-BlackGreenInk is super for this)